A phase-shifting interferometer with a laser diode (LD) has been applied to a joint-transform correlator. An LD six-stepping interferometer is insensitive to the changes in laser power associated with the current variation. A new method producing a joint-transform phase correlator (JTPC) is presented in which the phase in a joint-power spectrum (JPS) of two inputs is measured by the technique of LD phase-shifting interferometry. A charge-coupled device records the JPS those recording optical layout is an on-axis type by using a Mach-Zehnder interferometer. A single centered correlation is generated by the numerical Fourier transformation of the measured phase. A JTPC exhibits sharper correlation peak than the conventional JTC. The experimental results with a JTPC are shown.

A novel scheme of an interferometric microscope is proposed to visualize a geometrical spin-redirection phase image that represents the local inclination of micro surface structures of an object. The observed phase depends on the state of polarization and optical constants of the object material, which enables one to distinguish the spin-redirection phase from the conventional dynamical phase. A preliminary experiment was performed, and the phase images obtained were found to be consistent with those predicted by computer simulation based on a theoretical model.

The methodologies and tools used recently in animation are presented and their most significant problems connected with combining real and virtual world are recognised. It includes creating of computer graphics libraries of realistic 3D objects and describing the models of animation in 3D space. The presented measurement methodology simplifies the process of generation ofvirtual objects and gives as the result: shape and movement description ofthe monitored object. Optical structured light methods are proposed for gathering the information about a shape, deformations of shape and shifts of 3D objects. Authors apply the spatio-temporal approach, in which the spatial analysis of fringe pattern delivers information about initial shape of the object, while the temporal analysis of intensity variation I(t) in the given pixel provides information about shape variations and out-of plane displacement. I(t) is analysed by Fourier transform based method. Determination of rigid body motion of the objects is performed by photogrametry based marker tracking method. The methodology of measurement is presented together with exemplary experimental results.

A method for measurement of continuous displacements and deformations is presented. The method may be used in e.g. speckle interferometry, moire, structured light and other optical measurement methods based on evaluation of phase changes. The initial random phase of the interference pattern is either known or evaluated before displacement take place using e.g. phase shifting. The changing phase thereafter is achieved only from one image at a time by a least square algorithm. The technique can be used for measuring shape deformations such as transients and other dynamic events, heat expansion as well as other phenomena where it is difficult to accomplish phase shifting during deformation.

A coordinate transform method is proposed which enables the Fourier transform method to analyze interferograms including closed fringe patterns. According to the principle of the proposed method, closed fringe patterns in an interferogram can be converted to open fringe patterns by transforming the Cartesian coordinate system to a polar coordinate system. Phases corresponding to the open fringe interferograms can be obtained by analyzing the open fringe interferograms using the conventional Fourier transform method. Subsequently, the original phases corresponding to the closed fringe interferograms can be acquired by inverse coordinate transform. Computer simulation and experiments show that spherical wave fronts are accurately recovered by using the proposed method.

High precision measurements of nearly flat highly reflective surfaces present many problems when using a phase-measuring Fizeau interferometer. Since a coated reference surface is required to yield good fringe contrast with a high reflectance test surface, the interference fringes are likely to deviate from being perfectly sinusoidal. Utilizing phase-measurement algorithms that take data over a 2-wavelength range of phase shifter motion can help reduce the effects of errors due to nonsinusoidal fringes. If linear and 2nd-order phase shifter errors are present, the greater number of frames of fringe data can aid in making a better estimate of the phase. Eight algorithms that have been published in the literature are compared using simulations and experimental measurements. From this study, it was determined that a 12-frame algorithm having 60° (?/3) phase shifts developed by Surrel had superior performance when used with a Clapham-Dew type coated reference surface and a high reflectance test surface. Residual errors in the phase calculation were found to be reducible to a few thousandths of a wave peak-to-valley.

While phase-shifting interferometry is now used widely to map the deviations of optical surfaces from a reference plane or reference sphere, the accuracy of such measurements is limited by systematic errors due to several causes. It has been shown that these systematic errors can be minimized by a simple averaging technique. We present calculations of the residual errors in some typical cases, which confirm that, with this technique, the residual errors can be reduced quite easily to negligible levels.

Highly aspheric optical components are being used more frequently as increased demands are placed on optical system performance. The use of aspheric optics can simplify an optical design while increasing optical system performance. However, the effects of spatial distortion when testing fast off-axis optics can present a significant challenge to both designing the optical test-set and to post-processing the test data. Correcting for spatial distortion by post-processing the measured data is one approach that can be taken to increase the convergence rate when polishing an optic to a given prescription. This paper discusses the effects of spatial distortion at the exit pupil resulting primarily from the combined effects of geometric perspective distortion and mapping error. A software method for spatial distortion correction is presented along with the use of a distortion verification grid for verifying the accuracy of an applied distortion correction.

With the electronic industry being one of the most dynamic, in terms of new technologies, electronic packages have to be designed and optimized for new and ever more demanding applications in relatively short periods of time while satisfying electrical, thermal, and mechanical requirements, as well as cost and manufacturability. In addition, reliability and durability have to be taken into consideration. As a consequence, effective quantitative methodologies, such as optical and computational should be applied in the study and optimization of microelectronic components. In this paper, a hybridized use of nondestructive, noninvasive, remote, full field of view, quantitative opto-electronic holography techniques with computational modeling is presented. The hybridization is illustrated with a representative application, which shows that the combined use of opto-electronic holography techniques and computational modeling provides an effective engineering tool for nondestructive study and optimization of microelectronic components.

This paper presents a new kind of double illumination interferometer used for true radial in-plane displacement measurement with electronic speckle pattern interferometry (ESPI). The basic principles, some characteristics and implementation details are discussed. Basic algorithms for displacement and strain measurements are presented and implementation details are given. A very robust and portable device was built using this new kind of interferometer to measure outside the optical bench. This device has been successfully used for residual stress measurements in a very efficient way where the blind hole drilling technique is used in combination with the radial displacement field. Early results show a potential measurement performance comparable to the conventional blind hole method using strain gages. Measurement time is almost one order less than the strain gage based measurement system.

TV-holography or electronic speckle pattern interferometry (ESPI) is used for the detection of micro-deformations on a variety of optically rough surfaces. These deformations are often a result of processes in the whole volume. If the investigated object is, for example, composed of different layers the interaction between these layers can result in a deformation of the surface. Such effects are often seen on antique paintings and result in a net-like structure of cracks, the so-called craquelee. To understand these processes it is necessary to measure the movement of each layer separately. ESPI can be used for sub-surface deformation measurements on layered objects, when it is operated with a low-coherence light source like a superluminescense diode as used in optical coherence tomography. Interferometric information is only registered if the difference between the path length of object and reference beam is less than the coherence length. By changing the path length of one of the beams it is possible to select the region where deformations will be measured even if it is located below the surface, provided the light penetrates the material sufficiently. A serious problem is the separation of the coherent light and the incoherent background. This is performed by a combination of spatial phase shift (SPS) and Fourier filtering.

I have investigated induced diffraction gratings recorded by light intensity pattern in pure and dye-doped nematic liquid crystals antraquinone dyes (0.1 - 1% w/w), sandwiched between two coating glass plates covered by ITO conductive and polyimide orientation layers (low-angle rubbing, tilt 1.5 - 2°) under dc electric field. In dye- doped nematic liquid crystals high diffraction efficiency approaching 20 % were measured. Fast optical grating formation with times constant ? of 2 ms were observed. The dependence of grating formation on strength of applied dc electric field, cell construction and liquid crystal parameters, configuration of light polarization and nematic director orientation have been reported. These effects are very useful for dynamic holography.

The influence of unresolved speckles on the pixelwise modulation in phase shifting techniques has been investigated in recent publications by several authors. It has been shown that the number of points with sufficient modulation does not automatically decrease when unresolved speckles are used. However, the effect of unresolved speckles on the resulting phase map has not been examined. In this paper it is investigated how the averaging of speckles over the area of a pixel affects the validity of the phase resulting from phase shifting techniques. Special attention is given to the effect of unresolved speckles on phase singularities, since interferometric measurements with fully resolved speckles result in a phase map which contains a large number of phase singularities. Phase singularities are points where no phase value is defined, so that the appearance of singularities decreases the lateral resolution of the measurement. Additionally these points and their direct neighbourhood are a source of trouble for unwrapping algorithms. It is investigated how a slightly averaging of speckles alters the appearance of these problematic regions.

Shearography is a full field optical technique for measurement of surface strain. In multi-component shearography an accurate knowledge of the location of the source positions is required to resolve the displacement derivative components in three dimensions. Shadow Moiré using a linear grating is an established technique for measurement of angle of illumination. The grating pitch can be varied to change the measurement range and sensitivity, and sub-fringe processing is used to obtain the angle of illumination, with ambiguity if multiple fringes are present. Shadow Moire using a circular grating may also be used to measure angle of illumination. Multiple fringe processing is used to obtain the angle of illumination, with the sensitivity and measurement range again adjustable by varying the grating pitch. As the circular and linear gratings have different measurement ranges for the same grating pitch, they can be combined to extend the measurement range. In this paper circular, vertical linear and horizontal linear gratings have been combined to provide measurement of the position of the optical source in two directions with extended range and enhanced accuracy.

Shearography is a full field non-contact optical technique generally used for measurement of the derivative of the displacement of the surface on an object subjected to mechanical or thermal loading. This paper describes the use of shearography for surface slope and shape measurement. Correlation of interferometric speckle patterns obtained before and after displacement of the optical source generates correlation fringes which are, in general, a mixture of slope and carrier related fringes. Carrier fringes are generated when the source is displaced along the source-object optical axis and slope fringes are generated by movement orthogonal to the source-object optical axis. The sensitivity of the slope fringes to the object slope is determined by the illumination and imaging geometry, the optical wavelength, the applied shear and the magnitude of the source displacement. The slope fringes are distorted by the necessary off-axis illumination, so a correction is made by subtracting the slope fringes generated on a flat plate. Mathematically modelled and experimentally generated phase-stepped slope fringes are unwrapped and integrated to recover the object shape.

A measurement system constructed with a micro Fizeau interferometer and the spatial fringe analysis method is proposed to measure precisely a deflection of microstructures. The results of the deflection are given as the boundary condition of a FEM. A stress in the element is analyzed by the FEM. To confirm the validity of the principle, the experiment is performed with a macro model. The measuring optical system for the macro model is constructed with a projection moire system. Without any contacts, the stress map in the element can be estimated by this method. Comparing the result from this method with the result by strain gauges, it confirms that the accuracy of the estimation of the stress is less than 5 MPa in the macro model. On basis of results in the macro model, a stress in a micro cantilever can also be estimated.

In this study, the atomic force microscope( AFM) scanning moiré method is developed. The scanning lines in the AFM monitor are used as the reference grating. The reference grating interferes with the specimen grating, and forms a moiré pattern on the monitor. The formation mechanism of AFM moiré, the deformation measurement principle using this method are described in detail. The AFM scanning moiré method is used to measure the residual deformation of mica substrate after being damaged by the YAG laser, and the thermal deformation in a QFP type electronic package. The experiment results verify the feasibility of AFM scanning moire method and show its ability to measure the in-plane deformation in both micro-and nano-scales.

In view of applications of SiOxNy thin films in MOEMS technology, a study the optomechanical characteristics of this material PECVD deposited are investigated. To optimize the quality of SiOxNy layers we establish the relationship between the chemical properties, optical performances, micromechanical stress, and growth parameters of deposited films. To use the SiOxNy thin film for the core layer of a strip-loaded waveguide, we propose preparation conditions of SiOxNy that offers a low-loss optical waveguide with well-controlled refractive index, based on a low-internal stress multilayer structure .

The Ronchi test is a widely used tool in the optical shop, because of its capability of measuring wide-field profiles of optical quality surfaces through its important ray slope dynamic range. Although many applications have been reported (intraocular lenses, capillary flow measurements, etc.), they are usually limited to obtaining profiles of rotationally symmetrical surfaces, either spherical or aspherical. An easy to set-up Ronchi test technique based in geometrical optics principles has been developed at the CD6, which allows accurate and repetitive wavefront measurements of the topography of both rotationally and non-rotationally symmetrical optical quality surfaces. In order to demonstrate its capabilities, the technique has been applied to the profilometry of the toroidal concave surfaces present in common astigmatic spectacle lenses. Profiles of two sample surfaces at two different distances from the ruling to the sample have been measured with micrometric resolution. As toroidal surfaces are not rotationally symmetrical, both samples have been positioned with its principal meridians following different orientations, in order to demonstrate that the technique performs adequately not only for a range of distances from the ruling to the sample but also regardless how the sample has been oriented. The accuracy of the measurements is demonstrated through the comparison of the radius of curvature values obtained using the proposed Ronchi test technique, with reference radius of curvature values obtained using a high precision radioscope. The technique is shown to measure sub-micrometric surface features on toroidal surfaces by use of a combination of self-developed and commercial software, allowing the observation of surface profile details with extensions of just some tenths of nanometers in depth.

The wide scale inspection of extended technical components with respect to the recognition of typical surface features (shape, texture, roughness) needs the combined application of different measurement techniques with new tools for the consistent analysis and description of the measuring results. The new concept of scaleable topometry meets the demands of wide scale surface topometry. Controlled by the evaluation of scale-independent surface features based on fractal geometry, different measurement techniques with subsequent lateral and depth resolution are applied to the surface. The result is a complete description of the surface covering a wide scale taking into account special regions of interest. The choice and orientation of the special measurement technique is supported by a new feature extraction method called the fractal pyramid. The advantages of the new concept are demonstrated on several technical components.

White-light Vertical Scanning Interferometry (VSI) is a well-established technique for retrieving the three-dimensional shape of small objects. It has the advantage of non-contact measurement with absolute depth resolution at nanometer level repeatability. The technique has proven to be very effective in measurements of microstructures such as MEMS devices, surface texture, roughness, etc. However, it can only measure areas as big as the field of view of the instrument, usually not more than 15 mm, or a stitching algorithm must be applied. This slows down the measurements and often can be a source of errors. In this paper we present a modification of the technique permitting measurements at higher speeds while retaining the overall accuracy and repeatability of VSI. In the presented method the object is scanned laterally in front of an instrument with a tilted coherence plane such that the data is acquired continuously eliminating the need for stitching for elongated objects. One of the advantages of the proposed system is possibility of faster scanning speed with the use of a high speed CCD arrays. In the paper we present the principle of the method along with an experimental confirmation.

This paper describes a grating projection method using phase shifting technique for the measurement of surface profiles of three dimensional objects. In this kind of profilometry a grating with binary intensity distribution has been utilized in most of cases. And in these cases such problems are known as an error is caused due to the non-sinusoidal intensity distribution of the grating and another difficulty is also indicated that the period of the grating is required to be adjusted in accordance with the size and profile of the specimen. Here we propose to use a moire pattern which is produced by superposing two binary gratings. When two gratings are overlapped with an appropriate gap, the resultant moire pattern becomes closely sinusoidal in intensity distribution. Then, in the optical arrangement for profile measurement using a grating projection method, if one grating is rotated, the period of the pattern is varied arbitrarily. And if one or two of the gratings are moved in one direction, the formed moire pattern can be moved in one way to give necessary shifting of the phase. Surface profiles of some samples are measured to show validity of the moire pattern projection and utility of the prototype system.

A novel aperture connection method for measurement of surface with rotation axis is presented. This work is an extension of “Multi-aperture overlap-scanning technique (MAOST)” in a cylindrical coordinate system, by which a surface with rotation axis such as 360-deg shape can be accurately measured. The principle of MAOST is to make the adjacent sub-apertures partially overlapped, and then the relationship between each couple of adjacent sub-apertures can be obtained through the overlapped area to restrain the error propagation in patching these sub-apertures into an overall measurement result. So the high-precision mechanism and time-consuming system alignment is not required. Based on the inherent mapping relationship between the coordinate transformation operator and error vector, an iterative algorithm is presented, at the same time by which we can use a set of linear equations instead of non-linear equations to calculate the actual error vector. The computer simulation test shows the excellent results. The result of experimental test of a semi-cylinder surface is also presented.

Leendertz dual beam symmetric illumination - normal observation arrangement is widely employed for real time evaluation of in-plane displacement components as well as surface shape. Instead of observing along the optical axis, we have examined the Leendertz arrangement by observing the scattered light along the direction of illumination beams, and imaged as two separate images onto a photo sensor of a CCD camera. In this paper, we will show that the interference between the speckle fields generated from one of the illuminating beams with the specular reflection speckle fields from the second illuminating beam, is responsible for fringe formation along the directions of observation. The interferometer is a combination of two channels; each of which senses independently and simultaneously the information pertaining to either the in-plane displacement component of a deformation vector, or surface relief variation of a three dimensional object. A summary of possible information that can be extracted from the present arrangement is also highlighted. Experimental results using a four-frame phase shifting technique are illustrated.

In applications of surface profilometry with white light interferometry (WLI), the detection of the peak of the fringe contrast function is of prime importance. Several procedures have been proposed for the determination of the fringe contrast function. Fourier transform technique and phase shifting technique are two important methods. In the Fourier transform technique, the interference pattern is scanned to obtain the interference signal which is then subjected to filtering in the frequency domain. This involves two discrete Fourier transform operations. The phase shifting technique makes use of the algorithms introduced in the monochromatic interferometry for the calculation of the fringe contrast function. Both PZT and polarization phase shifters are proposed to be used for WLI. In this paper, it will be shown that polarization phase shifter offers some advantages over PZT phase shifter.

Anomalies in fringes pattern due to weak defect remain practically hidden when the object is subjected to load in between exposures. Increased load results in more number of fringes. In order to bring out the defective region vividly some procedure to reduce the number of undesired fringes should be adopted. Comparative speckle interferometry compares the response of the test object with that of the master object and the fringe pattern corresponds to the defect when the objects are identically loaded. Surface contours can also be compared. Use of phase shifting in comparative speckle interferometry would give the quantitative estimate of the residual difference.

A new concept of self-consistency is proposed in this paper and then a new phase-stepping algorithm based on it is presented. If the phase steps between the grabbed data frames are known, the phase distributions of every data frame can be calculated by the modified conventional phase-stepping algorithm. On the other hand, the phase steps between data frames can be calculated through the calculated phase distributions of every data frame above. The known phase steps and the calculated phase steps should be consistent. This is so called self-consistent concept .By means of iterative method, we can easily gain the accurate phase steps while calculating the measured phase distribution. Numerical simulations and experimental results verify the insensitivity of new algorithm to the phasestepping error and automatic calibration of phase shifter.

In interferometry measurement of density of plasma induced by pulsed laser, the external triggering signals are used to trigger flash lamp and Q-switch of main laser (Nd:YAG) and probing laser (N2 dye laser), in order to eliminate the jitter, a pre-delay unit and two delay units are used to get the delayed triggering signals for Q-switch of main laser and probing laser respectively, another innovative design is to replace the wollaston prism with a biprism, so that the polarizer and analyzer can be exempted, the loss of probing light can be lessened, and image of higher resolution can be achieved.

For the first time the possibility for parallel optical processing and recognition of interference patterns is shown. Sixty-four separated channels with multi-exposured holographic and low-cut filters are used The input interference patterns are calculated by finite element approach for penny-shaped crack in isotropic materials, surface defects and fault in laminate composite material. The set-up of an optical correlator for holographic recording of the filters and parallel processing of interference patterns is shown on Fig.l. High-resolution silver halide light sensitive material HP-650, made by the Bulgarian Academy of Sciences with different developers is used for holographic recording, creation of multiplicator and low-cut filters. Nine exposed holographic recordings were made for three different angles of rotation (-15 deg, 0, and +15 deg) and three different scales (-15%, 0, and +15%) of the interference patterns. Scale, shift and rotation invariant filtering has been obtained for a large angle of rotation of the input images The computer simulation, using a linear model of the system, is in good agreement with the experimental results. The differences could be explained by the nonlinearity of the multiexposure holographic recording For further development of the system and creation of the common filters for parallel optical processing of real two-dimensional interferometric data, a liquid crystal page composer and dynamic holographic recording in photorefractive materials are planed to be used.

In phase-shifting interferometry, a phase shifter usually has tilt shift error along with translational shift error during shifting. The pixels on the same interferogram can not be shifted by an equal amount. Thus the phase measurement errors can not be avoided, even when the translational shift error has been corrected effectively. However, based on the fact that phase shifts of all the pixels on the same interferogram are still kept on the phase shift plane. So by solving this plane the phase errors can be eliminated significantly In this paper, a new algorithm insensitive to both the translational and tilt shift errors of a phase shifter for phase-stepping interferometers is presented. The first order Taylor series expansion replaces the nonlinear equations in solving the phase shift plane, and by iterative, the accuracy can be guarantied. The simulative and experimental results show that phase measurement errors caused by both translation and tilt shift-error can be compensated significantly.

The precise angle monitoring is a very important metrology task for research, development and industrials applications. Autocollimator is one of the most powerful and widely applied instruments for small angle monitoring, which is based on the principle of geometric optics. In this paper we introduce a new precise angle monitoring system, Pencil-beam Angle Monitor (PAM), base on pencil beam interferometry. It’s principle of operation is a combination of physical and geometrical optics. The angle calculation method is similar to the autocollimator. However, the autocollimator creates a cross image but the precise pencil- beam angle monitoring system produces an interference fringe on the focal plane. The advantages of the PAM are: high angular sensitivity, long-term stability character making angle monitoring over long time periods possible, high measurement accuracy in the order of sub-microradian, simultaneous measurement ability in two perpendicular directions or on two different objects, dynamic measurement possibility, insensitive to the vibration and air turbulence, automatic display, storage and analysis by use of the computer, small beam diameter making the alignment extremely easy and longer test distance. Some test examples are presented.

The linear integer unconcerned phase-maps fringe projection profilometry has been used to measure the 3-D shape of object with discontinuous height steps. Linear integer unconcerned phase-maps are obtained by changing the angle of grating projected. The technique permits that the frequency of grating is not changed. An automated analysis of the fringe patterns is carried out by the Fourier transform method. Experimental results are presented that demonstrate the validity of the principle.

In phase-shifting interferometer, software processing method is a very important means to achieve high accuracy. By analyzing and simulating, it is indicated that only removing the effect of the error which has a spatial frequency of twice the fringe frequency in the result is not enough, especially in high accuracy measuring. The paper presents an averaging method to reduce the effect of errors. Testing results testify this averaging method is effective and robust.

Optical techniques that are used to measure displacements utilize a carrier. When a load is applied the displacement field modulates the carrier. The accuracy of the information that can be recovered from the modulated carrier is limited by a number of factors. In this paper these factors are analyzed and conclusions concerning the limitations in information recovery are illustrated with examples taken from experimental data.

Brake roughness and brake squeal are important issues/concems of customer satisfaction in the automotive industry. Brake roughness is a low frequency vibration while brake squeal is a high frequency noise. Some fundamental root causes of brake roughness are rotor runout, rotor surface flat spots, etc., which cause brake torque variation that in turn produces unwanted low frequency vibration. Brake squeal is a dynamic instability and nonlinear phenomenon that occurs in a frequency range of lKHz to 15KHz, which is in the range of sensitivity for the human ear. Squeal is usually caused by excitation of brake components brought on by slip-stick of the brake caliper pad material and rotor surface during brake actuation. This paper will provide an overview of examples that illustrate the application of holographic interferometry methodology to identify the root causes of brake concerns and verify engineering solutions.

The recording of holograms and the numerical reconstruction of the wave fields became possible with the development of high-resolution CCD-cameras and fast computers. This technique called Digital Holography is used for example in particle measurements and deformation analysis. Using an inline holography setup for particle measurements the particle distribution is calculated numerically from the recorded hologram. By varying the recording distance particles can be found in different depths of the analyzed volume. Using holographic film, the reconstruction process provides only the intensity of the recorded objects. With Digital Holography also the phase of the reconstructed object wave can be calculated. The question is whether the phase of the reconstructed optical field contains additional information compared to the intensity which can be used for example to find the depth coordinate with a much higher resolution. However the experiments show that the dimension of the recording system, the wavelength of the light used and the distance between object and recording system are still limiting factors for lateral and depth resolution. The presented paper gives an overview over phase reconstruction in particle analysis.

A method of visualising the 3-dimensional flow field within an opaque material has been developed using the principle of digital speckle photography combined with flash X-rays. The speckle pattern is achieved by seeding the specimen with a plane of lead filings and using X-rays to image the pattern before and during an impact event. Utilising a flash X-ray machine, the 2-dimensional components of displacement can be measured throughout the seeded plane. Thus, by repeating the experiment changing the times of the X-ray flashes and the location of the seeded plane, the full 3-dimensional displacement field within the specimen during the event can be deduced. The displacement sensitivity of the system is currently approximately 50 µm and the spatial resolution approximately 1 mm. Our current X-ray system gives an exposure time of 30 ns. The system has been successfully tested on polyester and cement samples but is here extended to the study of loose granular materials, in particular sand. This allows us to investigate material behaviour in a way not previously possible and in this paper we present the deformation caused by an impact from a fast-moving projectile.

Image formation in phase shifting digital holography is discussed by developing analytical formulation based on the Fresnel-Kirchhoff diffraction theory. Position of image plane and imaging magnification are derived. The influences of discrete sampling of the interference patterns by a CCD and numerical reconstruction on qualities of point images are investigated. Dependencies of the point images on the ratio of the minimum fringe spacing to pixel pitch of the CCD are numerically analyzed.

A new low-cost laser range finder using optical feedback interferometry has been developed. Our purpose is to design a high- accuracy sensor for short distances, the principle being based on using an optical fiber as a reference target. An accuracy of 10 \µm can be reached when measuring a distance of 2 cm between two targets located at around 4.5 m from the laser source.

A new laser range finder using optical feedback interferometry has been developed. Our purpose is to design a high-accuracy sensor for short distances, the principle being based on the use of a Mach-Zender interferometer to control the chirp of the laser diode. Experimentally, a distance to the target of 10 cm with an accuracy of ±50 µm has been determined.

Speckle interferometry (SI) is used for the measurement of the shape change of x-ray mirrors. Initially flat under thermal equilibrium, the mirror, or "thermal bender", is deliberately and adaptively bent by means of well-controlled temperature gradients. As the deflection of an optically polished surface can be obtained by a number of methods, the choice of SI and its subsequent advantages are discussed. Quantitative results are reported, referring to four kinds of tests: conformity, stability, sensitivity and repeatability tests. SI is recognized to meet the expectations: it provides a simple, complete, sensitive and accurate control of the shape of the bent x-ray mirrors.

An electronic 3D-shape measurement method has been developed by combining light-in-flight recording by holography (lif) with digital holography. Lif is a technique for direct visualization of the propagation of a short light pulse when it is e.g. intersecting a 3D-shaped object resulting in contour lines of the object. This is achieved by letting the reference beam be delayed in comparison to the object beam along a CCD-sensor. A Fourier-Fresnel algorithm numerically reconstructs the hologram. A Littrow mounted reflection grating in a Twyman-Green type interferometer set-up creates the optical delay between the object and the reference beam. The 3D-shape and the position of the object can be determined by combining the contour lines of the object together to a depth map. The recorded hologram from one point will be confined to a rectangular area on the CCD-sensor, where the delay between the reference and the object beam is within the pulse length of the laser. Due to diffraction limitation will the resolution be poor in the direction of the delay since the recorded rectangle area will have its shortest side there. The resolution can however be improved by making two recordings in two perpendicular directions. The two holographic images can then be combined keeping the best resolution of the two holograms. Increase of the resolution makes the lif method useful for more applications for shape and deformation measurements.

Current design, analysis and control engineering applications require effective experimental methodologies and tools for determination of displacement and strain fields as well as material characterization. The quality of experimental data obtained at industrial environment has to be sufficient to introduce them into further numerical analysis by FEM (CAE) or use immediately for product quality assessment process. In the paper we present two novel types of full-field laser extensometers based on four-beam, grating (moire) interferometry method. The first type of extensometers is designed for medium size field of view (6 x 4.5 mm ). It is integrated and works directly on a standard loading machine with the possibility to control the load on the base of local on-line strain measurements. It enables the measurements during static, monotonic and cyclic loads and full-field analysis of arbitrary sequence of images, The second type, based on the concept of waveguide interferometer, is designed for small size field of view (min. 0.18 x 0. 12 mm2). It is integrated with a standard optical microscope and it seems to be an excellent tool for local material studies and strain analysis of microcomponents. The waveguide extensometer presented includes miniature Twyman- Green interferometer, which allows to measure out-of-plane displacements. Both extensometers give high contrast and good quality interferograms, are insensitive to vibrations and work with simple, low cost laser diode. The capabilities of the extensometers are presented on the example of low cyclic fatigue testing of a steel specimen and local displacement and strain investigations performed at the ferritic-austenic steel sample and silicon microbeam.

In this paper the application of a time-division-multiplexed 3D-shearography instrument to the measurement of the surface strain of a non-planar object is described. The object under investigation is sequentially illuminated from three directions by three fibre coupled high power laser diode sources, and imaged onto a CCD camera through a single shearing interferometer. The pulsing of the sources, achieved by injection current modulation, is synchronised with the camera frame rate. The source pulsing schedule and image acquisition are controlled from a PC. The slope and shape of the object’s surface are measured by displacing one of the illumination fibres. Combining the slope and shape information with the deformation gradient measurement allows the surface strain to be determined.

Some recent applications of stereoscopic and two-dimensional digital speckle photography in experimental mechanics are presented. The examples include uses of both laser speckles and white light speckles. Topics covered are: control of the flow front when manufacturing fibre reinforced polymer composites by a closed molding process, measurement of internal deformations at high strain rates, and in opaque specimens, using flashed x-ray radiation. It is also shown how defocused laser speckles can be used to measure in-plane strain fields without the need of numerical differentiation and how laser speckles can be used to monitor the extent of the plastic zone in materials.

A double exposed reflection hologram and interferometry will be used to analyze the structural integrity of a carabiner. The first exposure will depict the carabiner unstressed, and the second will illustrate the carabiner under stress. After this, the carabiner will be broken and then compared with a developed hologram. The breaking strength will be determined using this method. A double exposed hologram of a control block - which moves approximately one micrometer - will be used to find a relationship between the amount of displacement and the weight applied to the carabiner. A hologram will then be made using the weight needed to move the carabiner one-micrometer to verify the relationship. Once the theory is validated, another carabiner, of the same model with little use, will be used as a test piece. Another double exposed hologram will then be taken of the new carabiner. Next the carabiner will be cycled approximately 500,000 times with a two Kilo-Newton load for duration of one week. Then one more double exposed hologram will be made after the cycles are completed. Once the holograms are developed, the two will be compared thus showing any changes in structural integrity if any are present. If changes in structural integrity are observed, a guide to determine if the carabiner being tested should be retired will be recommended.

An overview of the research in the field of interferometry as conducted within the Optics Research Group will be presented. The first interferometer that will be presented made use of sequential phase stepping, where later setups employed simultaneous recording of the required phase steps to calculate the phase distribution. The use of temporal phase unwrapping, and the benefits obtained by it, will be discussed. The latest developments will be indicated: fiber based interferometer with an accuracy goal of 0.1 nm and a single camera speckle shearing interferometer for defect detection and deformation analysis.

Shearography is an approved and powerful tool for the nondestructive inspection of industrial components with respect to material faults and technical imperfections. An application field of high interest is the in-service inspection of aircraft components. However, the non-cooperative character of the surface of various aircraft components to be inspected has to be taken into account carefully. This paper describes a complete test facility consisting of a shearographic sensor, adapted loading equipment for thermal and mechanical stressing and a new evaluation software ensuring a high sensitivity for fault detection. Furtheron a survey of the performance of the system is given on example of different aircraft components that shows the advantages of shearography in comparison with other inspection techniques, such as ultrasonics and thermography.

Laser light was revolutionary to optical testing methods. An optical method, shearography in combination with phase-shifting, has prooved as suited, easy- to- handle method to indicate deformations. Cartesian coordinates are usually applied, which are only an approximation when testing sections of toroidal objects. Tires approximative have a toroidal shape. By using polar shearing method deformations of the complete circumference of toroidal objects can be analyzed. An example of a defect in a tire will be shown. A small deformation of the tire by lowering the inner pressure permits dropping the critical unwrapping procedure. The pure modulo-2pi-image is used. The image processing procedure is modified to receive an absolute threshold for defect indication.

Human tooth structure in the oral environment is affected by considerable thermal fluctuations while consuming hot and cold, fluids and food materials. This paper describes the use of digital moire interferometric technique and Electronic Speckle Pattern correlation Interferometry (ESPI) to study the behavior of the functionally adapted dentine materials to thermal loads in its own plane and out of plane. Further, this study also highlights the advantage of optical techniques with enhanced sensitivity and spatial resolution to examine the whole-field thermal property gradients in an anisotropic biological material such as human dentine.

Interferometry as a highly sensitive non-invasive optical diagnostic tool needs intrinsically a thermal and mechanical well controlled environment. In opposition to the situation on ground space applications have severe constraints concerning volume, mass, modularity, etc.. This results in a more complex structure of an optical/mechanical set-up connected with stability problems, e.g. a folded optical path passing through more than one structural element in a more or less uncontrolled thermal environment. Thermo-mechanical deformations of the set-up can lead to significant errors in the resulting interferograms, especially for long term measurements, e.g. in crystal growth experiments. These deformations are subject to active compensation and alignment techniques, respectively. In this paper an active as well as a passive system developed for the compensation of optical effects caused by thermal induced deformations in space-borne interferometers is presented. The active system is able to detect wavefront tilting and curvature errors and to compensate them by means of piezoelectric driven optical components. An interferometer concept including Holographic Interferometry, ESPI and Shearing Interferometry and the misalignment detection as well as the compensation system are realised in a breadboard based on the interferometer design which will be integrated in the Fluid Science Laboratory (FSL) of the International Space Station (ISS). Extensive tests using the integrated interferometers show the suitability of the proposed compensation technique, not only for experiments in space but also for ground applications.

The collimation of strongly diverging laser beams emitted by diode lasers is performed with micro-optical components. In order to obtain a good beam profile high-quality cylindrical micro-lenses with a large numerical aperture compared to conventional lenses have to be applied. The characterization of these components using conventional interferometric techniques is costly or inaccurate with respect to the required accuracy of the lens shape. In conventional interferometry the resulting interferogram has to be imaged onto the CCD-target. The imaging lenses in the set-up can lead to additional wavefront aberrations and therefore to measurement errors. Additionally, conventional techniques are using phase shifting techniques for the evaluation of the interferograms. These techniques require at least three phase shifted interferograms which leads to a higher experimental and temporal effort. Digital Holography is an advanced optical diagnostic tool mainly used for surface deformation analysis, measurement of refractive index variations and particle analysis in transparent media: Holograms are stored electronically without any imaging optics and the reconstruction is performed by numerical methods. Due to the reconstruction process a numerical representation of the recorded wavefront can be evaluated including amplitude and phase from one hologram. In this paper Digital Holography as a measurement tool for the characterization of micro-optical components is presented, which has some advantageous properties with respect to other interferometric techniques. An analysis of the resolution of digital holography is performed in order to optimize the efficiency of this technique for the characterization of microlenses. The application of Digital Holography leads to a simple and robust measurement tool for shape measurement of microlenses which is demonstrated with two exemplary experiments characterising typical microlenses.

A measuring technique based on Ronchi test measurements has been developed in the Center for the Development of Sensors Instrumentation and Systems (CD6) in the Technical University of Catalonia, which allows the observation of submicrometric surface profiles on reflective concave surfaces. Being a grating technique based on a geometrical approach, it does not require any vibration-isolated environment, and it adequately performs under a range of known positions of the sample and regardless of its orientation, becoming a very robust surfacing technique. In order to achieve high sampling densities together with submicrometric accuracy, some enhancements were incorporated to the classical Ronchi test setup, including the use of CCD detectors, laser sources, multiple ronchigram acquisition and computing power. A multiple acquisition procedure has been used which allows to tailor the number of acquired data points to densities of up to 50mm-2. As an example, the technique has been applied to the measurement of three-dimensional topographies of spherical ophthalmic surfaces, although the technique is able to successfully manage non-rotationally symmetrical surfaces. Surface profiles of two pairs of spherical lenses identical to the standards of the ophthalmic industry have been measured showing how, although all lenses satisfactorily passed quality control procedures, in some cases their surface finishing was quite different, showing alterations along their manufacturing process which might lead to future quality control failures. The ability of the described Ronchi technique to measure submicrometric surface features, and to apply them to detect surface deviations in the manufacturing process, will be demonstrated.

This paper presents an approach to increase the understanding of errors and alignments in interferometrical contouring. In order to achieve a fully determined interferometrical set-up with a controllable alignment status, real existing interferometers are simulated with the help of a software package called the Virtual Interferometer (VI). It consists of a raytracing module, a measurement simulator for phase shifting evaluation and a statistics module to simulate the environmental aspects of interferometrical contouring (e.g. misalignments, surface errors of the optical components, phase shift errors). Additionally, a further software package for controlling the corresponding real interferometrical systems and a module for addressing two separate positioning systems each having 5 degrees of freedom was developed. With the help of the VI, two closely related aspects of interferometrical shape testing were examined. First, work in the field of testing aspheric surfaces with the use of Multiple Wavelength Interferometry (MWI) will be presented. New experimental results are introduced and the effect of aberrations due to strong surface slopes is discussed. Second, nulltests are presented that allow the measurement of aspheric mirrors like paraboloids and hyperboloids. In this application, especially the alignment of the complex interferometrical setup with its up to ten independent parameters was the main point of investigation. Both applications were analyzed with the VI in order to optimize the measurement methods with regard to alignment optimization and correction of error inducing aberrations. Then the optimized methods were applied in the real interferometrical systems for measuring various aspheric surfaces. Finally, future application for the VI will be discussed shortly.

Although interferometers are emerging strongly from the laboratory into the shop floor, many users are totally oblivious to potential errors that inevitably creep into the measuring process. Even a certificate of calibration that may come with an interferometer does undoubtedly not guarantee a constant measurement uncertainty for all time. The components will age, change, become maladjusted and, hence, make it necessary to periodically re-evaluate the present uncertainty. However, conventional calibration techniques are scarcely applicable to interferometers since these techniques are typically based on calibration standards with consideration of a common rule of thumb which demands for the uncertainty of the calibration instrument to be one tenth of the specified measurement uncertainty of the instrument being calibrated. Thus, in case of interferometers, a calibration standard is required with a remaining uncertainty which is not only far beyond current metrological and productional capabilities but also strongly influenced by environmental circumstances. Since it is extremely difficult to determine or even to predict the systematic errors that occur in a real interferometer, a Virtual Interferometer for simulation of typical measurements and examination of accurately specified error influences is currently being developed. The Virtual Interferometer may also help to obtain the measurement uncertainty that occurs in an actual measurement task. This can be achieved by applying several calibration measurements with the real interferometer and comparing them with the simulated results. Now the actual measurement task can be simulated yielding virtual measurement uncertainty that can be used as an estimation for the actual measurement uncertainty.

We have developed a new stroboscopic optoelectronic laser interferometry microscope (SOLEIM) methodology for rapid characterization of MEMS’ motion dynamics. Specifically, stroboscopic interferometric measurements of out-of-plane motions have been made on microengine components. In particular, measurements are presented for two microgears having 64 and 300 µm nominal diameters. These measurements are built on coherent light interferometry and phase shifting methods for whole field analysis. The microgears analyzed for this paper were rotated at speeds up to 360,000 rpm. In order for the most accurate measurement to be made, the strobe action must be a small fraction of the rotation cycle. The present system uses an AOM to strobe the light. The AOM has a rise time of about 5 nsec, and the electronic driver has a lower limit of 1 µsec for the “on” time of the strobe. In real terms, this limits, at the present time, our ability to freeze the rotational motion to a range of about 2.1° at 360,000 rpm. The range of out-of-plane motion is “controlled” by the gear-edge to substrate contact, approximately 1100 nm and 540 nm for the small and large gears, respectively. A new methodology was developed for measuring shape changes of rotating micro devices. This methodology permits quantitative and qualitative real-time whole field imaging, and provides capabilities for experimental determination of physical quantities such as out-ofplane displacements/tilts, or changes in shape, of high-speed micro devices.

Progresses in microsystem technology promise a lot of new applications in industry and research. However, the increased complexity of the microsystems demand sensitive and robust measurement techniques. Fullfield and non invasive methods are desirable to get access to spatially resolved material properties and parameters. This contribution describes a simple and fast interferometric method for the analysis of shape and deformation of small objects by optical means. These quantities together with a well defined loading of the components can be the starting point for a big variety of interesting material characteristics which can be evaluated by the use of physical models of the objects. Holographic interferometry and multiple wavelength contouring as well as multiple source point contouring are precise enough to fulfill the requests for precision and resolution in microsystem technology even on complex shaped structures with steps or gaps. A new adaptive, iterative algorithm is developed and applied to the measured results that allows the numerical evaluation of the phase data to get absolute shape and deformation information in Cartesian coordinates. Surfaces with holes, gaps and steps can be registered without any ambiguities. Digital holography as the underlying holographic recording mechanism is extremely suitable for small objects and lead to simple and compact setups in which the objects’ shape as well as their deformation behavior can be recorded. Experiments are described to show the great potential of these fast and robust measurement techniques.

In this paper, a novel compact optical diffraction strain sensor using medium density grating foil (500 lines/mm) and high-density diffractive grating (1200 lines/mm) is presented. The grating attached on the surface of a specimen is illuminated by a focused laser beam. The centroids of diffracted beam spots from the grating are automatically determined with two position-sensitive detector (PSD) sensors connected to a personal computer. The shift of second-order diffracted beam spots due to the specimen deformation is then detected. The influences of noise sources and system geometry on system performances, such as sensitivity, spatial resolution, and strain range and measurement linearity are discussed. Strain sensitivity of 1 micro-strain can be achieved. The spatial resolution for strain measurement of 0.4 mm is attainable. The system can be used for continuous measurement and for both static and dynamic test.

Digital micro-holo-interferometry is proposed in this paper for microstructure measurements. It is developed based on the in-line digital holography incorporated with long distance microscope. The system structure is theoretically explained with wavefront diffraction analysis. The compatibility of the long distance microscope with the specific requirements in micromeasurement is discussed. And the properties of the in-line configuration in improving system performance are studied. Theoretical analysis of the system is demonstrated by the experiments on a silicon microbeam for deformation determination.

The method of interferometric picture simulation of axial symmetrical gas flows for any initial tuning of two-beam interferometer is developed for digital interferometry. The method is based on polynomial representation of the theoretical density fields. Computer - generated interferograms are calculated for powerful explosion with central symmetry and conical supersonic flow field around sharp-tip cone when density fields depend on one parameter only. Results can be used in analisys of interferometric picture in the real experimental conditions. In addition, the comparison of experimental with computer - generated pictures is used to affirm adequacy of the theoretical model for description of visualized phenomena.

In the present investigation, holographic interferometry was utilized for the first time to determine the rate change of the alternating current (A.C.) impedance of aluminium samples during the initial stage of anodization processes in aqueous solution without any physical contact. In fact, because the A.C impedance values in this investigation, were obtained by holographic interferometry, electromagnetic method rather than electronic method, the abrupt rate change of the A.C impedance was called A.C impedance-emission spectroscopy. The anodization process (oxidation) of the aluminium samples was carried out chemically in different sulphuric acid concentrations (0.5-3.125 % H2SO4) at room temperature. In the mean time, the real-time holographic interferometry was used to determine the difference of the A.C.impedance of two subsequent values, dZ , as a function of the elapsed time of the experiment for the aluminium samples in 0. 5%, 1.0%, 1.5%, and 3.125% H2SO4 solutions. The A.C impedance-emission spectra of the present investigation represent a detail picture of not only the rate change of the A.C.impedance throughout the anodization processes , but also, the spectra represent the rate change of the growth of the oxide films on the aluminium samples in different solutions. Consequently, holographic interferometric is found very useful for surface finish industries especially for monitoring the early stage of anodization processes of metals , in which the rate change of A.C. impedance of the aluminium samples can be determined in situ .

An interference microscope based on a wavelength-to-depth encoding technique is presented. The wavelength-to-depth encoding is realized by using a diffractive lens and wavelength tuning. The coherence degree of the interference fields versus wavelength is analyzed. A depth discrimination of 0.71µm is obtained with 0.90 NA objective lenses. Experimental results of a four-level grating measurement are presented with results are comparable to those obtained with a Dektak profilometer and the same interference microscope using mechanical depth-scanning. The system is promising for fast, noncontact, high- resolution three-dimensional imaging.

Application of laser Michelson interferometers as the strainmeters for sensing of earthquake precursors is described. Earthquake precursors can appear as anomalous deformations (local irregular crustal movements and tilts, global slow periodical lithosphere oscillations) or anomalous changes of the Earth free oscillations in amplitude and frequency. The most perfect instrument with highest sensitivity to the crustal movements is the laser interferometer-strainmeter. The precursoral relative crustal movements have the order 10-6- 10-7 for irregular local strains and 2-3 orders less for slow global seismic oscillations. Laser interferometer sensitivity to the crustal movements is approved to reach about 10-12 and it is obviously enough for detection of any type of precursoral strains. Some results of two seismic stations equipped by the long-base laser interferometer-strainmeters and built in Russia, at the North Caucasus (Baksan canyon) and in the Ukraine, near the Black Sea (the Crimea peninsula) are analyzed. These stations make continuous monitoring to registrate the changes of crustal strains, investigate the total spectrum of the Earth free oscillations and dynamics of lithosphere slow deformations. The sensitivity of the instruments is so high that they registrate the earthquakes all over the world, and recent results are presented in this paper. There are some good approvals that the deformation precursors sensing is the most perspective way for the earthquake prediction, and the long-base laser interferometers-strainmeters demonstrate high possibilities in this application. Perspectives of development of the new laser interferometer-strainmeters based on Russia high optical technologies and unique design are discussed.

In this paper, an analytical method, which combines experimental and numerical studies, is reported to determine material properties of Nd: YV04. In the experimental investigation, a laser interferometer is proposed to measure the physical deformation of lasing materials. The numerical solution with the finite-element (FE) method is used to calculate distributions of temperature, stress and strain in the lasing crystal, and then Young’s modulus and Poisson ratio of Nd: YV04 crystal are calculated to be 133GPa and 0.33, respectively.